1. Field of the Invention
The present invention relates to clamps for electrical cables in general, and, more particularly, to a clamp for connecting a jumper cable to the post of a motor vehicle storage battery.
2. Background Art
Battery jumper cables are frequently used in the emergency starting of motor vehicles having discharged storage batteries. Such storage batteries have charge storage sections which store electrical charges with which to operate starter motors and other electrical equipment. The charge storage section may accidentally become discharged, in the event that some such equipment (such as headlights), is left energized, if there is a ground in the vehicle's electrical system, or if the battery is simply old and/or worn out.
Typical vehicle storage batteries have external terminals for both the positive and negative poles of the charge storage section. The external terminals typically take the form of short, slightly tapered posts made of a suitable metal, most typically lead or lead alloy. When the storage battery is installed in a motor vehicle, the posts of the battery are typically gripped by lead or copper cable clamps on the ends of electrical cables. Normally, one cable electrically connects a selected terminal of the battery to the electrical system of the vehicle, while the other cable electrically connects the other terminal of the battery to the ground provided by the bodywork of the vehicle. Some varieties of storage batteries have terminals which are flush with the case of the battery, and which are bored and tapped to receive a bolt. The bolt serves to fix a flat, doughnut-shaped cable connector against the terminal. As used in this description and the appended claims, the term "terminal" includes all such battery posts and terminals, either with or without the associated clamps or connectors attached thereto.
When a battery becomes discharged and is unable to start the motor vehicle, resort is frequently made to the use of jumper cables. A second vehicle, having a charged storage battery or an operating engine, is brought proximate to the first vehicle, and jumper cables are used to connect the battery of the second vehicle to that of the first vehicle so that the first vehicle can be started. The jumper cables serve to electrically connect corresponding terminals of the batteries of the two vehicles.
Conventional jumper cables typically comprise a pair of electrical cables, each having an alligator clamp on each end thereof. The alligator clamp, which is typically a large, spring-loaded, stamped metal clamp having serrated jaws, serves to grasp the terminal of the battery. These alligator clamps, while they have long been used, exhibit a number of inconveniences and disadvantages. Perhaps the single most serious disadvantage is the inability of such clamps to securely and immovably grasp the battery terminals; even when they are clamped about battery terminals, they are still easily moved and swiveled about. Often, such movement causes another part of the stamped metal alligator clamp to come into contact with the bodywork of the motor vehicle; if that clamp is secured to the positive terminal of the battery, severe sparking results. Not only does this severe sparking represent the potential for discharging the batteries and damaging the vehicles' electrical systems, but it also represents a significant safety hazard, inasmuch as such sparking may ignite hydrogen gases which emanate from the charge storage sections of batteries. Such alligator clamps are also easily knocked or pulled off of the battery terminals, especially when tension is applied to the jumper cables when attempting to connect them to the other battery, which is both inconvenient and frustrating for the operator. Still further, such conventional alligator clamps, despite their serrated jaws, sometimes grip the battery terminal with insufficient force and/or contact area to adequately penetrate the corrosion which is often present on the surface of the terminal, thus failing to establish effective electrical contact with the terminal.
The foregoing failings of conventional alligator clamps on battery jumper cables stem in no small part from their inability to apply an unyielding force to clamp the jaws about the battery terminal; the springs of the clamps are necessarily quite limited in strength so that an operator can overcome them with the strength of his hand, and, no matter how strong, the springs only serve to yieldingly bias the jaws closed about the terminal.
Another problem which is commonly encountered with conventional jumper cables concerns the connection of the clamps to the associated electrical cables. In use, the clamps are pulled and moved back and forth, both in the process of attaching the cables to battery terminals and in winding the cables for storage. Typically, the wire strands of the cable are simply gripped en masse in a crimped connection formed from an extension of the stamped metal alligator clamp. As the clamps work back and forth on the ends of the electrical cables, the individual wire strands fatigue and eventually break and fray. As the strands break, the ability of the electrical cable to carry current from one battery to the other is significantly reduced. Eventually, the clamp may separate completely from the end of the electrical cable, rendering the jumper cable useless.
Accordingly, there exists a need for a clamp for mounting a jumper cable in electrical contact to a terminal of a vehicle storage battery which grips the terminal securely and unyieldingly, so as to establish an effective electrical connection therewith, and so as to prevent the clamp from accidentally moving on, or becoming detached from, the battery terminal. Furthermore, there is a need for such a clamp which eliminates the fraying and breaking of the wire strands of the jumper cable, as well for such a clamp with which to replace conventional clamps on the ends of battery jumper cables which are frayed or broken.